ho14.l11_cd

# ho14.l11_cd - Lecture 11 Common Drain Stage(Source Follower...

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1 Lecture 11 Common Drain Stage (Source Follower) R. Dutton, B. Murmann Stanford University R. Dutton, B. Murmann 1 EE114 (HO #14) Common Drain Stage R. Dutton, B. Murmann 2 EE114 (HO #14)

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2 CD Voltage Transfer (1) () 0 1 = + + o i m gs i gs Ltot o v v g sC v R sC sC v Ltot Ltot gs m gs m i o R sC sC g sC g v v 1 + + + + = Ltot m gs m o C C g sC g v 1 1 + + = R. Dutton, B. Murmann 3 EE114 (HO #14) ( ) Ltot m Ltot gs Ltot m i R g s R g v 1 1 + + + o mb L Ltot sb L Ltot r || g || R R C C C 1 = + = Low Frequency Gain Ltot m m v R g g a 1 0 + = o mb L Ltot r || g || R R 1 = Interesting cases –R L →∞ , r o →∞ , g mb =0 • PMOS, source tied to body, ideal current source 1 0 = v a mb m m v g g g a + = 0 L →∞ , r o →∞ , g mb 0 • NMOS, ideal current source) (typically 0.8) R. Dutton, B. Murmann 4 EE114 (HO #14) –r o →∞ , g mb =0, R L finite • PMOS, source tied to body, load resistor L m m v R g g a 1 0 + =
3 High Frequency Gain () s z s a v v s a v i o v = = 1 1 0 gs m C g z = Ltot m C C R g p + + = 1 Three scenarios p Ltot gs |z|<|p| |z|>|p| |z|=|p| R. Dutton, B. Murmann 5 EE114 (HO #14) (infinite bandwidth !?) CD Input Impedance By inspection* Hint*: I=C gs (v i -v o ) ( ) ( ) ) s ( a sC C C s Y v gs gb gd in + + = 1 Gain term a v (s) is real and close to

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## This note was uploaded on 11/09/2009 for the course EE 114 at Stanford.

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ho14.l11_cd - Lecture 11 Common Drain Stage(Source Follower...

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